diff --git a/pom.xml b/pom.xml
index 689ada8..9af1cba 100644
--- a/pom.xml
+++ b/pom.xml
@@ -29,7 +29,7 @@
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
-            <version>4.12</version>
+            <version>4.13.1</version>
             <scope>test</scope>
         </dependency>
         <!-- https://mvnrepository.com/artifact/org.apache.commons/commons-dbcp2 -->
@@ -55,12 +55,22 @@
     <properties>
         <maven.compiler.source>1.8</maven.compiler.source>
         <maven.compiler.target>1.8</maven.compiler.target>
+        <encoding>UTF-8</encoding>
     </properties>
 
     <build>
         <testSourceDirectory>src/testapp/java</testSourceDirectory>
         <plugins>
-
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.1</version>
+                <configuration>
+                    <compilerArgs>
+                        <arg>-Xlint</arg>
+                    </compilerArgs>
+                </configuration>
+            </plugin>
             <plugin>
                 <artifactId>maven-jar-plugin</artifactId>
                 <version>3.1.0</version>
diff --git a/src/main/java/perfix/server/json/SynthSerializerFactory.java b/src/main/java/perfix/server/json/SynthSerializerFactory.java
index 880acbf..489bf7d 100644
--- a/src/main/java/perfix/server/json/SynthSerializerFactory.java
+++ b/src/main/java/perfix/server/json/SynthSerializerFactory.java
@@ -29,7 +29,6 @@ public class SynthSerializerFactory implements SerializerFactory {
     private static final String ROOT_PACKAGE = "serializer.";
 
     private final ClassPool pool = ClassPool.getDefault();
-    private final Map<String, CtClass> primitiveWrappers = new HashMap<String, CtClass>();
     private CtClass serializerBase;
 
     SynthSerializerFactory() {
@@ -43,15 +42,6 @@ public class SynthSerializerFactory implements SerializerFactory {
     void init() {
         try {
             serializerBase = pool.get(JSONSerializer.class.getName());
-
-            primitiveWrappers.put("int", pool.get(INTEGER));
-            primitiveWrappers.put("short", pool.get(SHORT));
-            primitiveWrappers.put("byte", pool.get(BYTE));
-            primitiveWrappers.put("long", pool.get(LONG));
-            primitiveWrappers.put("float", pool.get(FLOAT));
-            primitiveWrappers.put("double", pool.get(DOUBLE));
-            primitiveWrappers.put("boolean", pool.get(BOOLEAN));
-            primitiveWrappers.put("char", pool.get(CHARACTER));
         } catch (NotFoundException e) {
             throw new SerializerCreationException(e);
         }
@@ -74,13 +64,12 @@ public class SynthSerializerFactory implements SerializerFactory {
         }
         try {
             return tryCreateSerializer(beanClass);
-        } catch (NotFoundException | CannotCompileException | InstantiationException | IllegalAccessException e) {
+        } catch (NotFoundException | CannotCompileException | ReflectiveOperationException e) {
             throw new SerializerCreationException(e);
         }
     }
 
-    private <T> JSONSerializer<T> tryCreateSerializer(CtClass beanClass) throws NotFoundException, CannotCompileException, InstantiationException,
-            IllegalAccessException {
+    private <T> JSONSerializer<T> tryCreateSerializer(CtClass beanClass) throws NotFoundException, CannotCompileException, ReflectiveOperationException {
         CtClass serializerClass = pool.makeClass(createSerializerName(beanClass), serializerBase);
 
         addToJsonStringMethod(beanClass, serializerClass);
@@ -172,9 +161,8 @@ public class SynthSerializerFactory implements SerializerFactory {
     }
 
     @SuppressWarnings("unchecked")
-    private <T> JSONSerializer<T> createSerializerInstance(CtClass serializerClass) throws InstantiationException, IllegalAccessException,
-            CannotCompileException {
-        return (JSONSerializer<T>) serializerClass.toClass().newInstance();
+    private <T> JSONSerializer<T> createSerializerInstance(CtClass serializerClass) throws CannotCompileException, ReflectiveOperationException {
+        return (JSONSerializer<T>) serializerClass.toClass().getConstructor().newInstance();
     }
 
     /*